<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>如何让一个块级元素水平居中</title>
<style type="text/css">
<!--
#layout {
 background-color: #CCCCCC;
 width:400px;
 height: 240px;
 text-align: center;
 margin:0 auto;
}
-->
</style>
</head>
<body>
<div id="layout">此处显示  id "layout" 的内容</div>
</body>
</html>